Hydraulic actuator for a trip plow

ABSTRACT

A hydraulic actuator that can be used on trip plows to hold the trip blade in its operative downward position and to control the return of the trip blade after tripping. The actuator has a body with first and second ends. A piston rod reciprocates within the tube. A plate with a channel is positioned within the tube a spaced distance from the tube ends. The plate creates an oil reservoir between the plate and the piston rod. A reciprocating piston is positioned within the tube between the second end and the plate. A spring is mounted between the second end and the reciprocating piston and normally biases the reciprocating piston into engagement with the channel normally closing the channel. The piston rod moves in the direction of the plate when the trip blade hits an obstruction, forcing the oil through the channel moving the reciprocating piston and opening the channel allowing oil to flow into an oil chamber created between the reciprocating piston and the plate. The spring biases the reciprocating piston back to the normally closed position and forces the oil into the oil reservoir after the trip blade has cleared the obstruction.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.63/115,234 filed on Nov. 18, 2020, which is incorporated herein byreference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

NONE.

TECHNICAL FIELD

This invention relates generally to hydraulic springs and moreparticularly to hydraulic springs used on trip plows.

BACKGROUND OF THE INVENTION

Trip plows are well known. One example is their use on snowplows forplowing a roadway surface with snow and/or ice. Trip plows have a mainblade and a trip blade connected to the main blade. A linkage systemconnects the trip blade to the main blade and a spring forces the hipblade to the lowered operational position. When an obstrudion isencountered the trip blade trips to a raised inoperative position whichcompresses the spring. Tripping the trip blade prevents damage to theplow, the plow vehicle, and the driver. When tripped, the spring iscompressed. When the obstruction is cleared, the spring forces the tripblade back to its operative lowered position.

The problem with spring type trip blades is the size of the springs orspring rate needed to keep the trip blade in its operative position. Thespring rate must be high enough to keep the trip blade down against theroad surface to clear the road surface. With high spring rates, thestored energy of the spring when compressed is extremely high. When theObstruction is cleared, the stored energy is violently released which isloud and jarring to the plow, vehicle, and driver.

What is needed is a trip blade that requires a smaller spring and whichhas a controlled return of the trip blade to its operative positionafter tripping.

SUMMARY OF THE INVENTION

The present invention discloses a hydraulic actuator that can be used ontrip plows to allow a smaller spring to be used to hold the trip bladein its operative downward position and control the return of the tripblade after tripping. The hydraulic actuator has a body, shown as atube, with first and second ends. A piston rod reciprocates within thetube. A plate with a channel is positioned within the tube a spaceddistance from the tube ends. The plate creates an oil reservoir betweenthe plate and the piston rod.

A reciprocating piston is positioned within the tube between the secondend and the plate. A spring is mounted between the second end and thereciprocating piston and normally biases the reciprocating piston intoengagement with the channel normally closing the channel.

The piston rod moves in the direction of the plate when the trip bladehits an obstruction, forcing the oil through the channel moving thereciprocating piston and opening the channel allowing oil to flow intoan oil chamber created between the reciprocating piston and the plate.The spring biases the reciprocating piston back to the normally closedposition and forces the oil into the oil reservoir after the trip bladehas cleared the obstruction.

The spring can be much smaller than would be required if only acompression spring were used. The spring only needs to hold thereciprocating piston in its normally closed position. This force is afraction of the force required to hold the trip blade in its downwardoperating position because of the areas of the channel, nose, and thepiston head. If the diameter of nose is 1/25 the diameter of pistonhead, the spring would only need a spring rating of 1/25 of the normalspring rate required to force and hold the trip blade in its downwardoperative position. Also, the channel controls the retain of the oil tothe oil reservoir and returns the trip blade to its operating positionwithout the crashing that would result from a coil spring.

In this way, the trip blade is held at the desired trip force to ensurethat it engages the surface for snow and ice clearing. When tripped, thetrip blade can trip to rapidly clear an obstruction. When theobstruction is cleared, the trip blade can return to the workingposition under a slower controlled return without the jarring impact oftypical trip plows.

These and other features and advantages of this invention will becomemore apparent to those skilled in the art from the detailed descriptionof a preferred embodiment. The drawings that accompany the detaileddescription are described below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the actuator of the present invention.

FIG. 2 is a cutaway view of the actuator of the present invention.

FIG. 3 is a detail view of B in FIG. 3.

FIG. 3A is a second embodiment view of B in FIG. 3.

FIG. 4 is a perspective view of a trip plow with the actuators attached.

FIG. 5 is a partial perspective view of a trip plow with an actuatorattached.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

The actuator of the present invention is shown generally at 10 in FIGS.1 through 3. Actuator 10 has a tube assembly 12 with a piston rod 14extending from a first end 15. The piston rod 14 has a connector 11 atthe distal end and a piston head 13 at the proximal end.

A head cap 16 closes the first end 15. An end cap 18 closes the oppositeor second end 19 of tube assembly 12. The head cap 16 includes seals 20to seal against the rod 14. The seals 20 seal the opening 21 in the headcap 16 against the rod 14 to contain oil in the oil reservoir 23.

A plate 24 is housed within the tube assembly 12, a spaced distance fromthe first end 15 of the tube assembly 12. Plate 24 includes channel 26.The channel communicates fluid between the oil reservoir 23 and an oilchamber 25. Oil flows from oil reservoir 23 to oil chamber 25 as thepiston head 13 moves toward plate 24.

Channel 26 is normally closed by a reciprocating piston 28. Thereciprocating piston 28 is biased to the closed position by a spring 30.The reciprocating piston 28 includes seals 29 which seal against theinterior wall of the tube assembly 12. The seals 29 prevent oil in theoil reservoir 23 from flowing past the reciprocating piston 28 in thetube assembly area housing the spring 30.

In the disclosed embodiment, the plate 24 includes a check valve 32, seeFIGS. 2 and 3. The check valve 32 allows oil to flow from the oilchamber 25 to the oil reservoir 23 but not to flow from reservoir 23 tochamber 25. The check valve 32 empties any remaining oil from the oilchamber 25 into the oil reservoir 23 when the reciprocating piston 28nears the closed position. It should be understood that the majority ofoil in chamber 25 empties into reservoir 23 through channel 26. Itshould be appreciated that an additional seal, such as a rubber gasketor o-rings, can be added to the nose 34 and/or recess to enhancesealing.

A sealing nose 34 protrudes from the face 35 of reciprocating piston 28and partially enters channel 26 when the reciprocating piston 28 isclosed. In the disclosed embodiment, nose 34 has a truncated cone-shapedend which mates with the recessed opening 33 in channel 26.

A moveable plate 36 abuts against the end of spring 30. A bolt and jamnut 38 engage the moveable plate 36. The bolt and jam nut 38 can berotated to move the plate 36 within the tube assembly 12 to compress thespring 30 to change its tension against the reciprocating piston 28.

A capped opening 40 is provided for the addition of oil to the oilreservoir 23. In the disclosed embodiment, oil is added to reservoir 23when actuator 10 is assembled and then the opening 40 is closed. Innormal operation, additional oil is not required to be added. In otherwords, actuator 10 is a sealed system with a single charge of oil, andno additional oil is required. It will be appreciated that other ways ofcharging the actuator 10 are known and could be used.

A mounting ear 42 is provided on the exterior of the tube assembly 12for mounting the actuator 12.

With reference to FIG. 3A, a second check valve 50 is provided in thechannel 26. This is an alternative embodiment. In this embodiment, thecheck valve 50 facilitates the holding of the oil in the reservoir 23when the trip blade is in the operative position. The check valve 50works in the opposite direction to check valve 32. Check valve 50 onlytrips when the force exceeds the trip force.

In operation, the actuator is mounted to for example a trip plow 44, seeFIGS. 4 and 5. The mounting ear 42 would be mounted to the plow body 46and the connector 11 is mounted to the trip blade 48 as shown in FIG. 4,a number of actuators 10 could be used. As will be appreciated, a tripplow is a type of plow that has a trip blade 48 that pivots or movesupwardly when an obstruction is hit. This tripping feature prevents theplow or the vehicle from being damaged when obstructions are hit by theplow.

When trip blade 48 hits an obstruction, it is forced upward. This forcemoves the rod 14 into the tube assembly 12. The piston head 13 moveswithin the oil reservoir 23 forcing the oil through channel 26 againstthe sealing nose 34, moving the reciprocating piston 28 towards end 18and introducing oil into the oil chamber 25. Due to the impact forceacting on the trip blade 48 and the oil being forced through channel 26,the reciprocating piston 28 moves rapidly against the bias of the spring30 allowing the trip blade to clear the obstruction. The spring bias ofspring 30 is low compared to the force of the trip blade 48. The springbias of spring 30 is only enough to hold the reciprocating piston 28against the plate 24, when the trip blade 48 is in the operativeposition.

When the obstruction is cleared, spring 30 biases the reciprocatingpiston 28 back to its normally closed position against plate 24. The oilin the oil chamber 25 is forced back through channel 26 at a much slowerrate to refill the oil reservoir 23. A slower rate when compared to acompression spring releasing its stored energy. The nose 34 reseats intochannel 26. Residual oil in oil reservoir 23 is forced through the checkvalve 32 to ensure that the nose 34 can properly reseat. This isimportant to ensure that a proper trip force is required to trip thetrip blade 48.

The trip force, the initial force required to trip the trip blade 48 canbe set by adjusting the bolt and jam nut 38. The adjusting bolt and jamnut 38 are optional. The spring force can be pre-set at the factoryobviating the need for the adjusting bolt and jam nut 38.

It will be understood that the spring 30 can be much smaller than whatwould be required if only a compression spring were used. The spring 30only needs to hold the reciprocating piston 28 in its normally closedposition. This force is a fraction of the force required to hold thetrip blade 48 in its downward operating position because of the areas ofthe channel 26, nose 34, and the piston head 13. If the diameter of nose34 is 1/25 the diameter of piston head 13, the spring 30 would only needa spring rating of 1/25 of the normal spring rate required to force andhold the trip blade 48 in its downward operative position.

In this way, the trip blade 48 is held at the desired trip force toensure that it engages the surface for snow and ice clearing. Whentripped, the trip blade 48 can trip to rapidly clear an obstruction.When the obstruction is cleared, the trip blade 48 can return to theworking position under a slower controlled return without the jarringimpact of typical trip plows.

The foregoing invention has been described in accordance with therelevant legal standards, thus the description is exemplary rather thanlimiting in nature. Variations and modifications to the disclosedembodiment may become apparent to those skilled in the art and do comewithin the scope of the invention. Accordingly, the scope of legalprotection afforded this invention can only be determined by studyingthe following claims.

What is claimed is:
 1. A trip snowplow comprising: a plow and body: atrip blade mounted to said plow body, a hydraulic actuator connectedbetween said plow body and said trip blade, said hydraulic actuatorhaving a tube with first and second ends, a piston rod extending fromsaid first end, said piston rod having a piston head adapted toreciprocate within said tube; a plate having a first surface and asecond surface, said first surface spaced from said first end and saidsecond surface spaced from said second end, said plate positioned withinsaid tube a space different distance from said first end creating an oilreservoir containing oil between said plate and said piston head; achannel extending through said first and second surfaces of said plate,a reciprocating piston position within said tube between said second endand said second surface of said plate; a spring mounted between saidsecond end and said reciprocating piston said spring normally biasingsaid reciprocating piston into engagement with said channel normallyclosing said channel; said piston rod and said piston head moving in thedirection of said plate when said trip blade hits an obstruction, saidoil in said oil reservoir being partially forced through said channelagainst said reciprocating piston moving said reciprocating piston inthe direction of said second end and opening said channel allowing saidoil to flow into an oil chamber created between said reciprocatingpiston and the second face of said plate when said reciprocating pistonmoves in the direction of said second end, said spring biasing saidreciprocating piston back to said normally closed position and forcingsaid oil from the oil chamber into said oil reservoir after said tripblade has cleared said obstruction whereby said trip blade trips uponhitting an obstruction and is returned under controlled force to itsnormal position period.
 2. The trip snowplow of claim 1, furtherincluding an oil passage extending through said reciprocating piston anda check valve located in said oil passage; said check valve allowing oilto flow through said passage from said second side to said first side.3. The trip snowplow of claim 1, further including a second check valvelocated in said channel; said second check valve allowing oil to flowthrough said channel from said first side to said second side.
 4. Thetrip snowplow of claim 1, further including a nose extending from saidreciprocating piston in the direction of said channel, said nosenormally closing said channel.
 5. The trip snowplow of claim 4, whereinsaid nose has a truncated cone shaped free end.
 6. The trip snowplow ofclaim 1, wherein said channel has a first opening adjacent said firstsurface and a second opening adjacent said second surface.
 7. The tripsnowplow of claim 6, wherein said channel second opening is recessed. 8.The trip snowplow of claim 7, further including a nose extending fromsaid reciprocating piston in the direction of said second opening, saidnose normally closing said channel, said nose having a truncated coneshaped free end that is received within said second opening to normallyseal said channel.
 9. A hydraulic actuator comprising: a tube with firstand second ends, a piston rod extending from said first end, said pistonrod having a piston head adapted to reciprocate within said tube; aplate having a first surface and a second surface, said first surfacespaced from said first end and said second surface spaced from saidsecond end, said plate positioned within said tube a space differentdistance from said first end creating an oil reservoir containing oilbetween said plate and said piston head; a channel extending throughsaid first and second surfaces of said plate, a reciprocating pistonposition within said tube between said second end and said secondsurface of said plate; a spring mounted between said second end and saidreciprocating piston said spring normally biasing said reciprocatingpiston into engagement with said channel normally closing said channel;said piston rod and said piston head moving in the direction of saidplate when said trip blade hits an obstruction, said oil in said oilreservoir being partially forced through said channel against saidreciprocating piston moving said reciprocating piston in the directionof said second end and opening said channel allowing said oil to flowinto an oil chamber created between said reciprocating piston and thesecond face of said plate when said reciprocating piston moves in thedirection of said second end, said spring biasing said reciprocatingpiston back to said normally closed position and forcing said oil fromthe oil chamber into said oil reservoir after said trip blade hascleared said obstruction whereby said trip blade trips upon hitting anobstruction and is returned under controlled force to its normalposition period.
 10. The trip snowplow of claim 9, further including anoil passage extending through said reciprocating piston and a checkvalve located in said oil passage; said check valve allowing oil to flowthrough said passage from said second side to said first side.
 11. Thetrip snowplow of claim 9, further including a second check valve locatedin said channel; said second check valve allowing oil to flow throughsaid channel from said first side to said second side.
 12. The tripsnowplow of claim 9, further including a nose extending from saidreciprocating piston in the direction of said channel, said nosenormally closing said channel.
 13. The trip snowplow of claim 12,wherein said nose has a truncated cone shaped free end.
 14. The tripsnowplow of claim 9, wherein said channel has a first opening adjacentsaid first surface and a second opening adjacent said second surface.15. The trip snowplow of claim 14, wherein said channel second openingis recessed.
 16. The trip snowplow of claim 15, further including a noseextending from said reciprocating piston in the direction of said secondopening, said nose normally closing said channel, said nose having atruncated cone shaped free end that is received within said secondopening to normally seal said channel.